This invention relates to a key-operated locking mechanism, and more particularly, to a key-operated locking mechanism which is relatively pick-proof.
Locks, especially those used for doors, are susceptible to being relatively easily picked permitting unauthorized entry. Persons skilled in the handling of locks insert a specially constructed spring metal shim through the keyway and vibrate it from the keyway to rotate the latch controlled by the lock. This operation involves the application of lengthwise pressure on the shim simultaneously with rotation of it.
Conventional locks are of several types, one of such being a pin tumbler type lock. The pin tumbler lock comprises essentially a cylindrical shell within which rotates a cylinder plug operated by a key. A pin tumbler flange forms part of this cylinder shell and contains the usual pin tumbler bores, which are adapted to align axially with matching pin tumbler bores in the cylinder plug. Pin tumblers in the shell under pressure of springs are urged downwardly against the matching pin tumblers in the cylinder plug where they bottom against a longitudinal rib in the keyway of the cylinder. The cylinder plug cannot be rotated because of the partial projection of the pin tumblers from the bores of the shell into the bores of the cylinder. Following conventional practice, as the key is inserted, appropriate cutouts and projections thereon move the pin tumblers so that when the key is in place, the line of separation between the shell and cylinder plug pin tumblers will fall on the circumference of the cylinder plug defining a shear line and permit the cylinder plug to rotate in the shell.
The pin tumbler lock is easily picked by use of a special tool. The tool comprises essentially a shim which is inserted in the keyway and in turn pushes each of the pin tumbler pairs from blocking the shear line. As each of the pin tumbler pairs is so moved, the cylinder plug is rotated slightly to hold the pin tumblers in the non-blocking position causing the cylinder to eventually be rotated when all of the pin tumbler pairs are so moved. The picking of such locks can be accomplished by a single individual simultaneously using his two hands.
An object of our invention is to provide a pin tumbler lock which is difficult to pick.
Another object of this invention is the provision of a pin tumbler lock which is unlocked by the simultaneous manipulation of a plurality of independent blocking elements.
Still another object of our invention is to provide a pin tumbler lock which cannot be picked by a single individual.
Another object of our invention is to provide such a pin tumbler lock which is adaptable for a plurality of different type locks.
Yet another object of this invention is to provide such a lock which is interchangeable with standard lock cylinder housings so as to enable the invention to serve as a cylinder replacement.
Further and additional objects of our invention will become more apparent from the following description.